Acorn BBC Master 128, Service Manual

Page: 18 / 87

Master Series Service Manual
External I/O
Video display:- A 6845 CRT controller is provided to format the output
from ROB, composite video and PAL/NTSC connectors.
Analogue to Digital Converter:- A four channel A-D converter provides
10 bit binary conversions in 5ms. The absolute accuracy will depend on
the conditions of use.
Tape Interface:- Facilities to both save and retrieve data from audio
cassettes is provided.
Disc Interface:- Facilities to both save and retrieve data from
standard Shugart connected media. Filing systems are provided to
support data encoded in FM or MFM.
Network Interface:- Connection to the ECONET is provided by a 68B54
advanced data link controller. This is fitted on a daughter board and
may as such be fitted as an optional extra (standard on the ET
machine).
1MHz Bus:- The standard BBC computer 1MHz bus is provided.
External Second Processor:- An external second processor may be
connected. Selection of either internal co-processor or external
second processor is performed by software. Only one second or co-
processor can be active at a time.
Centronics Printer Port:- Connection is provided for the standard
parallel printer port configuration.
User Port:- The user port is an eight bit bidirectional bus with two
extra handshaking/serial lines. These are unbuffered.
RS423:- A serial RS423 port is provided.
Audio Output:- The output from the sound generator is amplified to a
speaker and provided at a phono style connector. Sound transfer to and
from the modem is provided.
Modem:- Connection for a modem with both dial pulse and dual tone
multi-frequency dialling is provided. This facility is provided to
support third party hardware.
13 Issue 1